Fluoropolymer dispersion coatings are known to exhibit outdoor durability, chemical resistance, and acceptable mechanical properties. The performance features of fluoropolymer dispersion coatings have led to their extensive use, for example, in the exterior building panel market. Fluoropolymer dispersion coatings are often applied by spray and roll coating or coil coating of flat sheet stock techniques. The coating film is formed by thermal fusion of the fluoropolymer particles in admixture with an acrylic resin.
Historically, fluoropolymer dispersion coatings exhibit a relatively high viscosity at relatively low volume solids content. Consequently, as much as 65 percent organic solvent by volume may be required to reduce the viscosity in order to facilitate application of the fluoropolymer dispersion coatings to a substrate.
The high level of volatile organic compounds (VOCs) of fluoropolymer dispersion coatings generally requires that the solvent vapors emitted by the wet film be captured and conveyed to a gas-fired incinerator or thermal oxidizer to destroy the VOCs. For example, the large amount of VOCs produced by coil coating flat metal sheet stock can limit the line speed of the coating application, or result in blistering of the film at higher film thicknesses. The incineration of the VOCs can also produce higher amounts of nitrogen oxide pollutants, particularly for fossil fuel-fired combustion processes.
As a result, it is desired to provide higher solids, lower VOC content liquid fluoropolymer coating compositions, which would allow for higher line speed application, reduced blistering tendency of the applied coating, and/or a reduced impact on the environment from VOCs. Furthermore, it would be considered by those skilled in the art to be an advance if such a coating composition could be achieved by the blending of relatively few ingredients while providing a simple formulation that would be easily manufactured and readily reproducible. Moreover, it would be advantageous to provide such coating compositions that include an acrylic polymer that does not cause yellowing and is derived from relatively inexpensive acrylic monomers.